Field of the Invention
The present invention relates to amide derivatives which can enhance the water-retaining ability of the horny layer of skin and have an excellent effect of improving skin roughness, intermediates for the production of such amide derivatives, external skin care preparations containing such an amide derivative, and methods of moisturizing skin by applying such skin care preparations to skin.
Discussion of the Background
The water content of the horny layer of skin is known to be critical for imparting moisture to the skin to maintain skin smoothness and softness. The retention of water in the horny layer is said to depend upon the presence of a water-soluble component in the horny layer, namely, a free amino acid, organic acid, urea or inorganic ions. In the above circumstances, these materials have been incorporated either singly or in combination in medicinal external skin care preparations or cosmetic compositions with a view toward improving or preventing skin roughness. In addition, many humectants having high affinity with water have also been developed and have been used for improving the skin roughness.
However, these humectants remain on the skin surface when they are applied to the skin, so that they serve to supply water to the horny layer. Moreover, the effects of such compounds are temporary, and they do not basically improve the water-retaining ability of the horny layer itself or prevent or cure skin roughness substantially.
Thus, there remains a need for compounds which can enhance the water-retaining ability of the horny layer of skin and can improve skin roughness. There also remains a need for intermediates useful for the synthesis of such compounds. In addition, there remains a need for skin preparations and methods for treating rough skin.